Thread safety

A ØMQ context is thread safe and may be shared among as many application threads as necessary, without any additional locking required on the part of the caller. Each ØMQ socket belonging to a particular context may only be used by the thread that created it using zmq_socket().

Multiple contexts

Multiple contexts may coexist within a single application. Thus, an application can use ØMQ directly and at the same time make use of any number of additional libraries or components which themselves make use of ØMQ as long as the above guidelines regarding thread safety are adhered to.

Messages

A ØMQ message is a discrete unit of data passed between applications or components of the same application. ØMQ messages have no internal structure and from the point of view of ØMQ itself they are considered to be opaque binary data.

ØMQ provides a mechanism for applications to multiplex input/output events over a set containing both ØMQ sockets and standard sockets. This mechanism mirrors the standard poll() system call, and is described in detail in zmq_poll(3).

Transports

A ØMQ socket can use multiple different underlying transport mechanisms. Each transport mechanism is suited to a particular purpose and has its own advantages and drawbacks.

Devices

ØMQ provides devices, which are building blocks that act as intermediate nodes in complex messaging topologies. Devices can act as brokers that other nodes connect to, proxies that connect through to other nodes, or any mix of these two models.

Error handling

The ØMQ library functions handle errors using the standard conventions found on POSIX systems. Generally, this means that upon failure a ØMQ library function shall return either a NULL value (if returning a pointer) or a negative value (if returning an integer), and the actual error code shall be stored in the errno variable.

On non-POSIX systems some users may experience issues with retrieving the correct value of the errno variable. The zmq_errno() function is provided to assist in these cases; for details refer to zmq_errno(3).

The zmq_strerror() function is provided to translate ØMQ-specific error codes into error message strings; for details refer to zmq_strerror(3).

Miscellaneous

Language bindings

The ØMQ library provides interfaces suitable for calling from programs in any language; this documentation documents those interfaces as they would be used by C programmers. The intent is that programmers using ØMQ from other languages shall refer to this documentation alongside any documentation provided by the vendor of their language binding.

C++ language binding

The ØMQ distribution includes a C++ language binding, which is documented separately in zmq_cpp(7).

Other language bindings

Other language bindings (Python, Ruby, Java and more) are provided by members of the ØMQ community and pointers can be found on the ØMQ website.

Authors

This ØMQ manual page was written by Martin Sustrik <moc.mpb052|kirtsus#moc.mpb052|kirtsus> and Martin Lucina <ks.anletok|otam#ks.anletok|otam>.

Resources

Main web site: http://www.zeromq.org/

Report bugs to the ØMQ development mailing list: <gro.qmorez.stsil|ved-qmorez#gro.qmorez.stsil|ved-qmorez>

Copying

Free use of this software is granted under the terms of the GNU Lesser General Public License (LGPL). For details see the files COPYING and COPYING.LESSER included with the ØMQ distribution.